DisplayPort communication is described in detail at least in “VESA DisplayPort Standard, Version 1.4,” released on Mar. 1, 2016, by VESA. This document, the content of which is known to one of ordinary skill in the art, is hereby incorporated by reference herein in its entirety, along with any earlier versions or related documents mentioned therein (collectively hereinafter “the DisplayPort specification”), for all purposes. The DisplayPort specification describes physical and logical techniques for communication between a DisplayPort source device which generates video (and, in some embodiments, audio) and a DisplayPort sink device which presents the video (and, in some embodiments, audio). The DisplayPort specification also describes topologies wherein one or more branch devices (which are similar to repeaters, splitters, or hubs) are present between the DisplayPort source device and the DisplayPort sink device.
The DisplayPort specification includes some limits on the length of a cable connecting the DisplayPort source device and the DisplayPort sink device, and also includes other specific requirements for the physical construction of the cable. For example, full bandwidth transmission over a passive cable is limited to a cable length of three meters. Further, the DisplayPort specification describes direct communication between the DisplayPort source device and the DisplayPort sink device, but does not allow any manipulation of the video or audio content between the DisplayPort source device and the DisplayPort sink device. The DisplayPort specification also assumes that a link is established between a given DisplayPort source device and a given DisplayPort sink device, and that if the given DisplayPort sink device is to link to a different DisplayPort source device, the link will have to be completely retrained.
What is desired are devices and techniques that allow DisplayPort source and sink devices that otherwise comply with the DisplayPort specifications to communicate over an extension medium despite the transmission distance limits and media requirements of the DisplayPort specifications. It is also desired to provide devices and techniques that allow seamless switching between presenting content from a first DisplayPort source device to presenting content from a second DisplayPort source device such that re-training the link to the DisplayPort sink device is not conducted.